Performance evaluation in running – Part 3: Energy expenditure during running.

This is the third part (the first was about VO2max, while the second was about the energy expenditure during rest) of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!

In terms of total energy expenditure is it more expensive running a 10 km race at 10 km/h or at 20 km/h? If we don’t consider the air friction component and if the race is run without any pace variation (steady state), the answer is: the total energy requirement is approximately the same!

The reason lies in the linear relationship between oxygen consumption and running speed. As a rule of thumb, during horizontal running the energy cost is about 1 kCal/kg/km. Thus, the energy cost of running 10 km for a 70 kg individual averages 700 kCal, regardless of running speed.

Having an ergospirometer, as explained in the previous Part 1 and Part 2, allows to know the relative contribution of Carbohydrates and Lipids in the energy transfer system; in Figure 1 the data are put together in a graph, and the main results can be described as follows:

  • the whole-body energy requirement increases up to 15-20 times above resting levels (purple curve);
  • for this athlete, between 6 and 10 km/h is evident the formation of a plateau where the ratio between Fats and Carbs contribution is constant;
  • training to extend the plateau is something to focus on, since the energy contribution of Fats is more than double of the Carbs’ one (9 kCal/g vs. 4 kCal/g);
  • the higher the speed, the lower the Fat’s contribution;
  • training at low speeds is a good way to “teach” the body to use the Lipids as energy source;
  • doing a Conconi test will allow the athlete to know exactly the different “fuels” contribution at his anaerobic threshold;
  • Proteins contribution is not taken into account, as explained in Part 2.
Figure 1 – Energy expenditure during running.

We are working on the fourth part, wich will be published after the next test session. Meanwhile…keep on training, people!

Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
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Performance evaluation in running – Part 2: Carbs, Fats and Proteins as Energy for living.

This is the second part (the first was about VO2max) of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!
During exercise the whole-body energy requirement increases 20 to 30 times above resting levels, but what are the relative contribution of Carbohydrates, Lipids and Proteins in the different energy transfer systems?
First of all, we need to define the above-mentioned “resting levels”: the BMR (Basal Metabolic Rate) is the amount of energy expended daily by humans and other animals to sustain vital functions in the waking state. Under controlled laboratory conditions, after at least 3 hours from the last light meal and without prior physical activity, the RMR (Resting Metabolic Rate) can be measured. The TDEE (Total Daily Energy Expenditure) can be divided as follows:
  • RMR accounts for 60 to 75% of TDEE;
  • thermic effects of eating account for around 10%;
  • physical activity accounts for the remaining 15 to 30%.
The first part of the ergospirometry is exactly the measurement of the RMR: without taking into account the Proteins’ contribution (being far enough from the last meal and without doing any prior physical activity allow this approximation), the machine can split the energy expenditure between Carbohydrates and Lipids measuring ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. There are some generalized equations to predict the Resting Daily Energy Expenditure (if anyone is interested, please contact me and I will write something more specific), but the direct measurement is always the most accurate solution.
As an example, in the Table presented below a set of typical data resulting from the RMR analysis with the ergospirometer is shown.

 

Table 1 – RMR analysis data.

 

The third part will be about the energy expenditure during exercise. Meanwhile…keep on training, people!
Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
Science and Training:
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Performance evaluation in running – Part 1: the VO2max.

This is the first part of a journey into the evaluation of the runner’s performance, made possible with the big support of Mark Henninger (himaxx Centre for Altitude Training – Berlin, Germany), that provided the ergospirometer, the treadmill, the hypoxic chamber and his knowledge for the tests. Thanks Mark!

The MET (Metabolic Equivalent of Task) is a physiological measure that expresses the energy cost of physical activities. It is defined as the ratio of metabolic rate during a specific physical activity to a reference metabolic rate (set by convention to 3.5 ml  O2/kg/min):

 
 
The reference metabolic rate just mentioned, is the expression of an individual’s body capacity to transport and use oxygen during exercise and it is called VO2 (milliliters of oxygen per kilogram of bodyweight per minute [ml/kg/min]). The maximum reachable value of VO2 describes the maximum capacity to transport and use oxygen during an incremental exercise and it is called VO2max. Various methods are available to predict the VO2max value, but the most accurate values can only be obtained with a measurement.
 
Figure 1 – VO2max measurement through an ergospirometer and a treadmill. 
 
The ergospirometer (it can be seen in Figure 1) is used to measure ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air during a graded exercise test (in this case performed on a treadmill, but it can be done on a cycle ergometer or on a rowing ergometer, depending on the reference sport): the  VO2max is reached when oxygen consumption remains at steady state despite an increase in workload (see Figure 2).
 
Figure 2 – VO2 & HR vs. speed (from rest to maximum speed).

 

In Figure 3 is possible to see the plateau created by the VO2 and the HR, when reaching the maximum values.

 

Figure 3 – VO2 & HR vs. speed (detail).
 
An average untrained man will have a VO2max of around 45 ml/kg/min, while women’s values are typically 10-15% lower. These values can improve with training (altitude training is a common way, for elite athletes, to try improving the VO2max values) and decrease with age, even if the degree of trainability is very variable: some individuals may double the initial values, while some others will never improve. Elite male runners can generate up to 85 ml/kg/min and female elite runners can generate up to 77 ml/kg/min, even if higher values are reported in literature.
 
The second part will be about the energy expenditure’s splitting between fats and carbohydrates. Meanwhile…keep on training, people!
 
Here you can find a list of my running-related posts. Now shut down the notebook and have a run!
Science and Training:
Races: